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PO'friend' functions and << operator overloading: What is the proper way to overload an operator for a class?
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Id
2828280
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AcceptedAnswerId
2828320
AnswerCount
3
ClosedDate
CommentCount
0
CommunityOwnedDate
CreationDate
2010-05-13T15:59:23.970
FavoriteCount
20
LastActivityDate
2016-07-25T15:45:57.153
LastEditDate
2016-07-25T15:45:57.153
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0
OwnerUserId
280698
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PostTypeId
1
Score
18
ViewCount
54301
LastEditorDisplayName
user6288471
text
Body
In a project I'm working on, I have a <code>Score</code> class, defined below in <code>score.h</code>. I am trying to overload it so, when a <code><<</code> operation is performed on it, <code>_points + " " + _name</code> is printed. Here's what I tried to do: <pre><code>ostream & Score::operator<< (ostream & os, Score right) { os << right.getPoints() << " " << right.scoreGetName(); return os; } </code></pre> Here are the errors returned: <pre><code>score.h(30) : error C2804: binary 'operator <<' has too many parameters </code></pre> (This error appears 4 times, actually) I managed to get it working by declaring the overload as a friend function: <pre><code>friend ostream & operator<< (ostream & os, Score right); </code></pre> And removing the <code>Score::</code> from the function declaration in score.cpp (effectively not declaring it as a member). Why does this work, yet the former piece of code doesn't? Thanks for your time! EDIT I deleted all mentions to the overload on the header file... yet I get the following (and only) error. <code>binary '<<' : no operator found which takes a right-hand operand of type 'Score' (or there is no acceptable conversion)</code> How come my test, in main(), can't find the appropriate overload? (it's not the includes, I checked) Below is the full score.h <pre><code>#ifndef SCORE_H_ #define SCORE_H_ #include <string> #include <iostream> #include <iostream> using std::string; using std::ostream; class Score { public: Score(string name); Score(); virtual ~Score(); void addPoints(int n); string scoreGetName() const; int getPoints() const; void scoreSetName(string name); bool operator>(const Score right) const; private: string _name; int _points; }; #endif </code></pre>
Tags
<c++><class><operator-overloading><friend><friend-class>
Title
'friend' functions and << operator overloading: What is the proper way to overload an operator for a class?
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UserOwnerUserId
1. USFrancisco P.
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